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Two species of water insects are behind the development of more efficient desalination membranes.
Surely, on a day in the beach, you may have noticed those insects that seem to walk effortlessly over the water. Probably, they belonged to the halobate species, creatures that harness the superficial tension to walk on the water as it were dry land. Their secret is a type of mushroom-shaped microtextures covering their cuticles and hairs. These trap microbubbles of air that keep them afloat. This kind of structures, also found in the water springtail, have inspired scientists at the King Abdullah University of Science and Technology in the development of a new water desalination membrane. Indeed, saltwater from the seas can provide us with many resources.
Super-water-repellent perfluorocarbon membranes have been in use for some time in a desalination process known as membrane distillation, which allows capturing water molecules as vapor. Despite the efficiency of this process to desalinate water, membranes do have their own issues: they are expensive, non-degradable and are prone to clogging and malfunctioning at high temperatures. These obstacles drove the researchers of the Jordan university to look for a perfluorocarbon-free alternative. And that is when they set their sights on said insects to create a membrane able to capture gases when submerged.
Initially, the team created bioinspired silicon wafers with pores narrowing at their inlets and outlets. The tests showed that the gas-capturing qualities of the material were retained for over six weeks. Following that, they replicated their design on a cheaper material, easily manufactured, like methyl methacrylate (PMMA). The final prototype can remove 100% of the salt in water for more than 90 hours. Besides its production advantages, the design is eco-friendlier. Now, the next step is to assess the technology’s industrial scalability.
Over the last few years, proposals for new desalination technologies have been put forward, some of them featuring in our page. However, besides developing new techniques to improve the efficiency of the process, one of the remaining challenges is processing the brine generated by desalination, which is usually pumped back into the sea and can cause environmental disruption as well as being power-hungry. At the MIT they have just proposed a new technology solution that transforms the brine into other chemical compounds such as sodium hydroxide, also known as caustic soda. Besides its applications in the chemical industry, this compound allows optimizing the desalination process by using it in the pretreatment of water, which modifies its acidity and prevents membrane clogging. Caustic soda could also be sold, thus improving the profitability of the plants. Finally, the technology envisioned by MIT could also obtain hydrochloric acid, a substance used to clean the machinery of desalination plants and as a catalyzer in the production of hydrogen.